The present invention relates to an averaging temperature responsive device usable in an air duct for measuring the average temperature across the duct of air moving therethrough and, more particularly, to such an averaging temperature responsive device which can alternatively be used as a point sensor.
Sensing temperature of the air moving through air ducts has historically been an essential ingredient in air conditioning and heating systems within buildings. The prior art has typically employed a resistance type sensor such as a Balco resistance as a sensor for sensing the temperature of the air moving through the duct. Unfortunately, the temperature profile of the air across the width of the duct may not be a constant so that the sensing of the temperature at any specific point across the width of the duct may not yield the true temperature of the air moving through that duct.
In order to accurately sense the actual temperature of the air moving through an air duct in an air conditioning and/or heating system, the prior art developed averaging temperature sensors for sensing the average temperature across the duct of the air moving through the duct. These prior art sensors comprise a long hollow tube having holes along the length thereof for permitting air at various points across the duct to enter the tube and to flow along the length of a tube to a sensor. By the time the air reaches the sensor, it will have been mixed enough to insure that the sensor will sense the average temperature of the air entering the slots at the various points along the length of the tube.
The use of holes along the length of these prior art tubes, however, does not allow for optimized temperature averaging. Moreover, these prior art averaging temperature responsive sensors cannot also be used as point sensors for those applications which require point sensing rather than averaging sensing.